Over temperature protection system for a gas turbine

ABSTRACT

A system to protect the turbine against transient high temperatures during the ignition period of a gas turbine. The protection system measures the pressure or flow rate of the fuel entering the turbine. If the pressure or flow rate exceeds a value which will produce an over temperature condition, a signal is sent to a fuel shutoff valve to interrupt the fuel flow to the turbine.

United States Patent Kiscaden 1 Sept. 18, 1973 [54] OVER TEMPERATURE PROTECTION 3,630,023 12/1971 Lazar et al. 60/3928 T SYSTEM FOR A GAS TURBlNE 7 2,862,355 12/1958 Davis et al..... (SO/39.14 2,761,284 9/1956 Malick 60/3928 T UX [75] Inventor: Roy W. Kiscaden, Springfield, Pa. [73] Assignee: Westinghouse Electric Corporation, Primary Examiner-Al Lawrence Smith Pittsburgh, Pa. Assistant Examiner-Robert E. Garrett [22] Filed Jan 27 1972 Attorney-A. T. Stratton et al.

21 A 1. No.: 221 184 1 pp 57 ABSTRACT 52 us. Cl 60/39.l4, 60139.28 T 60/223 A system P the turbine against transient high 51 Int. Cl. F026 7/26 temperamres during the ignim" Period gas [58] Field of Search 60/39.l4 39.28 T bine- The Pmtectim System measures the Pressure 60/223 flow rate of the fuel entering the turbine. if the pressure or flow rate exceeds a value which will produce an over [56] References Cited temperature condition, a signal is sent to a fuel shutoff UNITED STATES PATENTS valve to interrupt the fuel flow to the turbine. 3,382,671 5/1968 Enni ISO/39.14 4 Claims, 2 Drawing Figures AIR 2\ ,32 l 27 AND AND 28 39 TIMER 1 234 AND TO 1 IGNITION 1 4| -46 TRANSFORMER AND OR I 37 w III e 4s COMBUSTOR EXHAUST Patented Sept. 18, 1973 AIR-1 25 26 2?\ AND AND I39 I TIMER 1 34 I 7 AND 7 TO F IGNITION 41 -46 TRANSFORMER AND OR FUEL l5 F|G.|

TO COMBUSTOR BACKGROUND OF THE INVENTION DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in detail and particularly to It is of considerable importance to sense the tempera- 5 1, mere is Show" diagrammatically a single Shaft ture of the hot motive fluid, or products of combustion, as they enter the gas turbine to prevent the components therein from overheating. The gas turbine is extremely sensitive to overheating during the ignition period, when it is operating at about percent of synchronous speed, because a relatively small increase in fuel flow and/or fuel pressure to the combustion chamber of the gas turbine produces a relatively large increase in the temperature of the turbine parts. The most critical area in the turbine is the flow path of the hot motive fluid and more specifically the turbine blading. Commonly, the motive gases are measured by a plurality of thermocouples disposed either at the inlet to the turbine blade path or at the outlet thereof. Thermocouples mounted at the inlet to the turbine blade path, however, provide inaccurate indications of average temperature readings. Thermocouples at the outlet of the turbine blade path tend to give more accurate average temperature readings. However, the major disadvantages of using thermocouple devices in either the inlet or outlet temperature path is the time delay involved, i.e., by the time the temperature of the gases is measured and the signal is sent to close the fuel shutoff valve, the blade path has already been subjected to the high temperature transient condition. Repeated high temperature transients greatly increase the stress concentration in the blades, which can eventually cause blade failure.

Therefore, it would be desirable to devise a temperature protection system which would anticipate the over temperature condition and shut off the supply of fuel to the turbine to protect the turbine from a high temperature transient.

SUMMARY OF THE INVENTION The following disclosure relates to a gas turbine power plant and more specifically to a system to protect the turbine against high temperature transient conditions during the ignition period. The system includes a sensing device which measures either the pressure of flow rate of the fuel entering the turbine during the ignition period. If the sensing device measures a pressure or flow rate value which will produce an over temperature condition, a signal is sent to a comparator device, such as a digital computer. The comparator device then sends a signal to the fuel shutoff valve to interrupt the flow of fuel to the turbine before the over temperature condition occurs.

What is disclosed then is a system to protect the turbine against a high temperature transient condition by anticipating the condition and preventing the condition from occurring.

DESCRIPTION OF THE DRAWINGS axial flow gas turbine power plant or unit 10. The power plant 10 includes a compressor 1 l, a combustion chamber or combustor 12, and a turbine 13, the turbine rotor and compressor rotor being connected by a common shaft 15. The turbine 13 drives the compressor 11, and the shaft 15 extends from the compressor 11 and is connected to a load 16, which may be an electrical generator. Fuel is supplied through conduit 19 from any suitable source, to the combustion chamber 12, where it is mixed with pressurized air from the compressor 11 to fonn a combustible mixture which is ignited producing hot gases used to drive the turbine 13. A control valve 21 is disposed in the fuel conduit 19 to regulate the flow of fuel to the combustion chamber 12 during the ignition period and may also be used to con trol the quantity of fuel flowing to the combustion chamber during normal operation of the unit 10.

As shown in FIG. 1, a portion of a programmed digital computer 23 is provided with a plurality of signals. One signal is an analog input 25, which represents the speed of the rotor of the unit 10 during the ignition period, which is approximately 20 percent of the synchronous speed during this period. Another input signal 26 represents the position of the fuel selector, i.e., whether liquid or gaseous fuel is being utilized. A further input signal 27, monitors the position of the control valve 21 and still another input signal 28, indicates the position of a manual override switch which serves as a preignition hold, which allows the unit to be cranked without introducing fuel and igniting the combustible mixture. The analog input 25 and the inputs 26, 27 and 28 are fed into an AND gate 30. The output signal from the AND gate 30 is fed to a second AND gate 32. The signal from the AND gate 32 becomes an input signal to AND gate 34 and a solenoid valve 35. The solenoid valve 35, as shown in FIG. 2, operates the control valve 21 via a pneumatic conduit 37.

The output of the first AND gate 30 is fed to a programmed timer 39. The output from the timer is fed to another AND gate 41 and to the AND gate 34. The output signal from AND gate 34 becomes an input signal to operate the ignition transformer (not shown).

A sensing device 45 produces a signal representative of the pressure or flow rate of the fuel flowing in conduit 19 and provides an input to the AND gate 41. The output signal of the AND gate 41 is then directed to an OR gate 46. Other trip signals 48 such as over speed, high temperature, and loss of lubricating oil pressure, are also fed to the OR gate 46. The output signal from the OR gate 46 goes to the AND gate 32 and cooperates with the output signal from the AND gate 30 to 0perate the fuel control valve 21 through the solenoid valve 35.

As shown in FIG. 2, the solenoid valve 35 comprises a coil structure 50,.creating a magnetic field within coil 51, and a horizontally extending armature 52 pivotally connected to one end of a vertically extending rod 53. The other end of the rod 53 is pivotally connected to the base portion of housing 54 of the solenoid valve 35. A stem 56 extends horizontally from the bottom portion of the rod 53 and a plug 57 is secured to the end thereto, the plug 57 being outside of the housing 54. A

second stem 58 is secured to the middle portion of the rod 53. A plug 59 is fastened to the end of the stem 58 and is disposed within the housing 54. The housing 54 has an outlet port 61, an inlet port 62 and an outlet port 64 on the opposite side of the housing 54. In one position, when the coil 51 is energized, the armature 52 and vertical rod 53 move from left to right, the plug 57 closing the outlet port 61 and plug 59 opening the inlet port 62. In the other position, (which is that shown in FIG. 2) the coil 51 is deenergized and a spring 65 returns the rods 52 and 53 from right to left. Plug 59 closes port 62 and plug 57 opens port 61. Besides the solenoid valve 35 shown, other suitable devices well known in the art may be utilized.

The outlet port 64 of the solenoid valve 35 is fluidly connected to a diaphragm 21a of valve 21 to allow pressurized air to act on the diaphragm 21a to overcome the bias of a spring 65 to move the valve stem 22 vertically and regulate the flow of fuel through conduit 19. Thus the control valve 21 fails safe and closes upon loss of air pressure.

The sensing device 45 which provides a signal to the computer representative of the rate of flow of fuel, as shown in FIG. 2, is a pressure sensing device, however other flow responsive devices could be utilized. The sensing device 45 comprises a housing structure 67, a diaphragm structure 68 responsive to pressure in conduit l9, and a movable, on-off momentary switch 70 adapted to close when engaged by the diaphragm structure 68 to provide an electrical signal when the fuel pressure reaches a predetermined value, which is representative of a predetermined fuel flow sufficiently high to cause over heating if allowed to continue during the remainder of the ignition period. As previously stated, any signal representative of fuel flow rate over a predetermined value may be utilized to anticipate an over temperature condition in the turbine; thus any device capable of producing such a signal could be used in place of the pressure sensitive device as shown in the drawings.

In operation, the rotor of the unit is cranked by an outside power source and the rotor is brought up to lgnition speed, which is commonly about percent of synchronous speed. During the ignition period, the analog input signal 25 representing 20 percent of synchronous speed is fed into the computer 23 or any other comparative device, and into the first AND gate30. Also fed into the AND gate are signal 26, which is indicative of the fuel selected; signal 27, which is indicative of the position of the control valve 21; and signal 28, which is indicative of the position of the manual override switch. If all of these input signals are received, a signal is sent to the second AND gate 32. The output signal from the AND gate 30 also goes to the ignition timer 39 which will operate for a period of approximately 30 seconds to provide the proper ignition signal. The output signal from timer 39 is fed to AND gate 34 which provides an output signal which is fed to the ignition transformer (not shown) provided that there is an input to AND gate 34 from AND gate 32. The output signal from the timer 39 also goes to the AND gate 41 as an input signal thereto. Also fed into AND gate 41 is input signal 44, which is an electrical input responsive to a fuel flow rate which anticipates an over temperature condition in the gas turbine 13. If there is an input signal 44 plus an input signal from the timer 39 the third AND gate 41 sends a trip signal to the OR gate 46. Other trip signals 48 are also sent into the OR gate 46, and any one of these signals will produce an output signal which cooperates with the output signal from AND gate 30 to cause the control valve 21 to close and shut off fuel to the combustor. AND gate 34 is so related to AND gate 32, timer 39 and the ignition transformer that the ignition transformer is deenergized when a trip signal which closes the control a valve 21 occurs during the time interval when the ignition transformer would normally be energized.

During a no trip ignition cycle, there is no signal from the computer 23 to cause the solenoid valve 35 to deenergize and close the control valve 21, there is no output signal from the OR gate 46 and the input to the AND gate 32 is incomplete as AND gate 32 only functions when it receives a signal simultaneously from AND gate 30 and OR gate 46.

Referring to FIG. 2, it can be seen, therefore, that when the coil 51 is energized, passageway 62 is open providing pressurized air to the conduit 37 to cause the diaphragm 21a to move downwardly causing the valve 21 to open, thus providing a fail safe fuel control system. During the ignition period, about 30 seconds, and in the embodiment shown in FIG. 2, the pressure of the fuel flow is sensed in the sensing device 45. If the flow rate is such that an over temperature condition will occur, the diaphragm 68 is raised to engage switch 70. This causes an electrical trip signal to be sent to the computer 23 (FIG. 1). Upon receiving the trip signal from the sensor 45 the AND gate 41 sends a trip signal to the OR gate 46 if simultaneously AND gate 41 receives a signal from the timer indicating the turbine is in the ignition period. Upon receiving an input trip signal for AND gate 32 or upon receiving any other trip signal 48, the OR gate 46 in turn sends a trip signal to the AND gate 32 if simultaneously with receiving a signal from the OR gate 46 AND gate 32 receives a signal from AND gate 30, a signal is sent to the solenoid valve 35 causing the solenoid valve 35 to deenergize, to close the control valve 21 which cuts off the fuel supplied to the combustor 12.

Referring to FIG. 2, energizing the coil 51 opens port 62 and closes port 61 causing pressurized air to enter port 62 and flow through line 37 to the diaphragm 21a and operate against the bias of the spring within the valve to move the valve stem vertically upwardly to block the flow of fuel to the combustion chamber and protect the turbine against over temperature during the ignition period. The turbine is thus shut down and the problem causing the over temperature condition is corrected and the start up procedure would once again proceed in a normal manner. As previously noted, other means can be used to anticipate an over temperature condition such as any suitable flow rate device (not shown).

Therefore, what is disclosed is a temperature protection system which anticipates the over temperature condition in the turbine 13 and shuts off the supply of fuel to the combustor to protect the turbine from a high temperature transient during the ignition period.

Although one embodiment has been shown, it would be obvious to those skilled in the art that different embodiments of the invention may be made without departing from the spirit and scope thereof and therefore it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a gas turbine power plant having a rotor structure rotatable at a low speed during a cranking period and at an intermediate speed during an ignition period, a system for protecting the rotor structure from an over temperature transient condition, said system comprising in combination:

means responsive to the quantity of fuel supplied to the turbine during the ignition period,

means to interrupt the flow of fuel to the turbine,

signal applying means,

said means responsive to the fuel supplied providing a signal to said signal applying means when the quantity of fuel supplied corresponds to a quantity which will produce an over temperature condition in said turbine,

said signal applying means being adapted to activate said means to interrupt the flow of fuel to said turbine.

2. The system recited in claim 1, wherein the means responsive to the fuel supplied and the means for interrupting the flow of fuel are disposed in a fuel conduit upstream of the turbine, and

said signal applying means comprises a solenoid valve which activates the means for interrupting the flow of fuel.

3. In a gas turbine comprising at least one combustion chamber, a rotor structure, said rotor structure being rotatable at a low speed during a cranking period, at an intermediate speed during an ignition period, and at a high speed during an operating period, and a system for protecting the rotor structure from a high temperature transient condition, said system comprising:

pressure sensing means responsive to the pressure of the fuel flowing to said combustion chamber during said ignition period, said pressure sensing means providing a signal representative of the rate of flow of fuel to said combustion chamber,

means to interrupt the flow of fuel to said combustion chamber,

means for applying said signal to said means to interrupt fuel flow when said signal reaches a value corresponding to a rate of flow which will produce an over temperature condition in said turbine, if said rate of flow were allowed to continue.

4. In a gas turbine comprising at least one combustion chamber, a rotor structure, said rotor structure being rotatable at a low speed during a cranking period, at an intermediate speed during an ignition period, and at a high speed during an operating period, and a system for protecting the rotor structure from a high temperature transient condition, said system comprising:

flow rate sensing means responsive to the rate of flow of fuel to said combustion chamber during said ignition period, said flow rate sensing means providing a signal representative of the rate of flow of fuel flowing to said combustion chamber,

means to interrupt the flow of fuel to said combustion chamber,

means for applying said signal to said means to interrupt fuel flow when said signal reaches a value corresponding to a rate of flow which will produce an over termperature condition in said turbine, if said rate of flow were allowed to continue. 

1. In a gas turbine power plant having a rotor structure rotatable at a low speed during a cranking period and at an intermediate speed during an ignition period, a system for protecting the rotor structure from an over temperature transient condition, said system comprising in combination: means responsive to the quantity of fuel supplied to the turbine during the ignition period, means to interrupt the flow of fuel to the turbine, signal applying means, said means responsive to the fuel supplied providing a signal to said signal applying means when the quantity of fuel supplied corresponds to a quantity which will produce an over temperature condition in said turbine, said signal applying means being adapted to activate said means to interrupt the flow of fuel to said turbine.
 2. The system recited in claim 1, wherein the means responsive to the fuel supplied and the means for interrupting the flow of fuel are disposed in a fuel conduit upstream of the turbine, and said signal applying means comprises a solenoid valve which activates the means for interrupting the flow of fuel.
 3. In a gas turbine comprising at least one combustion chamber, a rotor structure, said rotor structure being rotatable at a low speed during a cranking period, at an intermediate speed during an ignition period, and at a high speed during an operating period, and a system for protecting the rotor structure from a high temperature transient condition, said system comprising: pressure sensing means responsive to the pressure of the fuel flowing to said combustion chamber during said ignition period, said pressure sensing means providing a signal representative of the rate of flow of fuel to said combustion chamber, means to interrupt the flow of fuel to said combustion chamber, means for applying said signal to said means to interrupt fuel flow when said signal reaches a value corresponding to a rate of flow which will produce an over temperature condition in said turbine, if said rate of flow were allowed to continue.
 4. In a gas turbine comprising at least one combustion chamber, a rotor structure, said rotor structure being rotatable at a low speed during a cranking period, at an intermediate speed during an ignition period, and at a high speed during an operating period, and a system for protecting the rotor structure from a high temperature transient condition, said system comprising: flow rate sensing means responsive to the rate of flow of fuel to said combustion chamber during said ignition period, said flow rate sensing means providing a signal representative of the rate of flow of fuel flowing to said combustion chamber, means to interrupt the flow of fuel to said combustion chamber, means for applying said signal to said means to interrupt fuel flow when said signal reaches a value corresponding to a rate of flow which will produce an over termperature condition in said turbine, if said rate of flow were allowed to continue. 